I have a TP-Link modem/router that is having difficulty providing a strong signal to my master bedroom, which is about 45 feet and several walls away. I have looked at several range extending solutions, but the cheapest would be to try replacing the 3 dBi antennas with these 9 dBi ones.

Do these larger antennas work, or are they more of a hoax? I have no experience on the matter and if it's money wasted then I might as well put that towards a better solution.

They work, but you have to understand how they work. They work generally by changing the shape of the radiation pattern. Router is only putting out so much energy so all you can do with that energy is shape it slightly differently. If you want the same pattern "just bigger", you need a router that puts out more energy or a booster that adds more power to your existing router.

I'd just run a cable in to your deadzone and set up an AP with the same SSID, encryption and password. It's the wireless client's job to pick the best AP. It should work just like cell phones do, hopping from tower to tower. Just make sure they're on different channels.

If you can't find a cheap access point, just get any ol' second hand router and turn DHCP off.

It is probably possible to purchase a multi-directional antenna with more gain. More gain means more sensitivity which means more range in every direction. You would need to first determine the db of gain of your existing antennas. If you can then find antennas with a higher db number than the ones you currently have, that will likely give you more range.

A few months back i replaced my Linksys WRT54GL for a E2000. Both have custom firmware.
The new router is great. I finally get what i pay for. Internet speed that is. Looking at the wireless signal. The WRT54GL fitted with high gain 7DBI antenna's did give me full wifi signal bars on my phone and tablet. Using the E2000 which does not have external antenna's i am lucky if i get one bar.
I live in a 3 story concrete house. Router is on the first floor in my bedroom. Before i did use a Linksys range extender but that thing was a b#tch to install correct and often gave me trouble using portable devices in the house.

I must say i did oc the shit out of that router and did fiddle with same settings but looking at what i got then and now i would say they do help a bit.

That's one thing that irks me about a lot of router manufacturers. They ditched external antennas to make the routers look good and the only way to upgrade the coverage is to add an AP or use a range extender/repeater. At least Amped Wireless keeps external antenna on all their stuff. Thier USB adapters even can have the antennas upgraded!

In the TP-LINK modem/router, does it have a menu dealing with transmitter to boost the signal strength? My Westell has that and so does my ATT. Remember not to set it at the maximum because in time it will burn out the unit. Typically on a power scale of 0-10, 8 is the ideal setting.

In the TP-LINK modem/router, does it have a menu dealing with transmitter to boost the signal strength? My Westell has that and so does my ATT. Remember not to set it at the maximum because in time it will burn out the unit. Typically on a power scale of 0-10, 8 is the ideal setting.

^ lol. no. antennas are just antennas, nothing much. its not bad, its silly. like installing lights on the ground instead of the ceiling XD

to power a more dbi antenna you will need a beefier driver/amplifier.

these antennas work by changing the physical characteristics of the wave its outputting, i.e. the amplitude of the wave. more amplitude = more energy reqd, so you will need a better amplifier.

a better idea is to place it at the corner of a room, and have a DIY parabolic reflector installed on it. cheap, wont cost more than 10$.

this being said, i have cheap ass USB accesspoint that i use as a wifi transmitter and i can get signals upto 35ft away without drop in power or ping. this too through 12"thick brick mortar walls and without any parabola.